The ESP package contains the source code for the Enforced Sup-Populations system written in C++. ESP is an extension to the SANE algorithm that segregates the neurons into sub-populations, one for each hidden unit in the networks being evolved. This allows neuron specializations to form more rapidly through constrained mating and enables the system to evolve recurrent networks. This package applies ESP to a non-Markov version of the double pole balancing problem. This is a difficult control task that requires short-term memory. For more details on ESP and/or the double pole system, see this paper on ESP or others found under Neuroevolution Methods and Applications.